Update to musl 1.1.22.

Update to musl 1.1.22.

Most of the changes are in threads, TLS, dynamic linking, and other
features wasi doesn't yet use, but there are some bug fixes in code
wasi does use.

atanl.c - local changes no longer needed as they've now landed upstream.

include/alltypes.h.in - Upstream now makes FILE a complete type in
pre-C11 mode. For WASI, this level of pre-C11 strictness isn't as
important, and having multiple incompatible definitions of _IO_FILE
that are kept separate only by clever use of translation unit
boundaries can confuse some tools, so stick with the incomplete type.